Coronary artery disease (CAD), which is the end result of the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium, remains the number one cause of disability and death in modern industrialized countries. In 2005, the estimated direct and indirect cost of CAD in the US is $393.5 billion. In the US in 2001, nearly 900,000 Americans experienced a new or recurrent heart attack, or acute myocardial infarction.
Stenosis, or narrowing of the cardiac arteries, is usually caused by plaque in a blood vessel. Plaque forms when cholesterol, fat and other substances build up in the inner lining of an artery. This process is called atherosclerosis. For assessing the hemodynamic relevance of a stenosis, in addition to the degree of stenosis, the relationship to the myocardial region of the coronary arteries is of particular interest.
With the advent of a new generation of imaging modalities, such as multi-slice scanners, like the Somatom Sensation 64 or the Somatom Definition (available from Siemens AG, Munich, Germany), and similar devices, cardiac computerized tomography (CT) has become a non-invasive alternative for imaging coronary arteries. CT imaging, with or without intravenous iodine-based contrast, can reliably visualize cardiac anatomy
A conventional association of the coronary arteries with the myocardial regions may be made using the “Standardized Myocardial Segmentation and Nomenclature for Tomographic Imaging of the Heart” in the form of so-called polar maps and by the 17-segment model of the American Heart Association (AHA), as set forth in an AHA Scientific Statement (2002). FIG. 1A shows the recommended left ventricular segmentation and associated descriptive nomenclature, and FIG. 1B shows the association of the coronary arteries with each of the 17 myocardial segments. However, this association has been caveated with the recognition that there is tremendous individual variability in the location of the coronary vessels. This model is based on statistical data and thus cannot necessarily reproduce the high anatomical variability of the coronary anatomy of an individual patient.